Activity 5: Investigating Weight Gain and Weight Loss

Conservation of Mass

• (Except in nuclear reactions) the total mass of of the materials (solids, liquids, and gases) involved in any change in matter stays the same.

Tracing Matter Process Tool

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solidg

g

g

g

g

Wetting a Sponge

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid30 g

20 g

g

g

g

What is your prediction of the weight ofthe wet sponge?

Wetting Vermiculite

What is your prediction of the weight ofthe wet Vermiculite?

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid40 g

30 g

g

g

g

Wetting a Sponge

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid30 g

20 g

g

50 g

g

Prediction that follows Conservation of Mass

Wetting Vermiculite

Prediction that follows Conservation of Mass

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid40 g

30 g

g

70 g

g

Your Predictions and Measurements

• When you measured the mass of the wet sponge and Vermiculite, how accurate were your predictions?

• Do you think conservation of mass applies to wetting the sponge and Vermiculite?

• Did the sponge and Vermiculite gain weight when you added water?

Drying a Sponge

What is your prediction of the weight ofthe dry sponge?What happened to the mass of the water?

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid50 g

g

g

g

g

Drying Vermiculite

What is your prediction of the weight ofthe dry Vermiculite?What happened to the mass of the water?

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid70 g

g

g

g

g

Drying a Sponge

Prediction that follows Conservation of Mass

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid50 g

g

20 g

30 g

g

Drying Vermiculite

Prediction that follows Conservation of Mass

Matter Inputs

Matter Outputs

Gasg

Liquid

Solid

Process:

Gas

Liquid

Solid70 g

g

30 g

40 g

g

Your Predictions and Measurements

• When you measured the dry mass of the sponge and Vermiculite, how accurate were your predictions?

• Do you think conservation of mass applies to drying the sponge and Vermiculite?

• Did the sponge and Vermiculite lose weight when you dried them out?

A Student Drinking Water

What is your prediction of the weight ofthe student after s/he drinks the water?

Matter Inputs

Matter Outputs

Gasg

Liquid

Student

Process:

Gas

Liquid

Student50.0 kg

600 g

g

g

g

Watering Your Plants

What is your prediction of the weight ofthe cup, soil, and plants after watering?

Matter Inputs

Matter Outputs

Gasg

Liquid

Plant in cup

Process:

Gas

Liquid

Plant in cup

150 g

10 g

g

g

g

A Student Drinking Water

Prediction that follows Conservation of Mass

Matter Inputs

Matter Outputs

Gasg

Liquid

Student

Process:

Gas

Liquid

Student50.0 kg

600 g

g

50.6 kg

g

Watering Your Plants

Prediction that follows Conservation of Mass

Matter Inputs

Matter Outputs

Gasg

Liquid

Plant in cup

Process:

Gas

Liquid

Plant in cup

150 g

10 g

g

160 g

g

Final Discussion Questions

1. Look back at the questions you answered before starting this activity. Do you now have different answers to any of the questions?

2. Do you think that conservation of mass applied to all the changes that you measured? Why were the masses you measured before and after sometimes different?

3. You can see that the measured weight of something can vary a lot depending on how much water is in the system. How could we tell whether plants are gaining dry weight (not just water) when they grow?