Lab Activity #10: Mixing and Melting Ms. Twardowski Tan: Science Central Middle School

A review of the Particle Model (fill in the blanks!) ALL objects and substances are made from _____ ______. These particles are _____ in motion! These particles have Kinetic _____.

A review of the Particle Model (fill in the blanks, again!) Particles of water in a ‘hot’ sample have _____ amounts of KE. The TOTAL amount of KE in the particles in called H____ E____. The AVERAGE amount of KE in the particles is called T_____.

In this Lab (Part A-Case 1)… In this lab we will mix particles of water from a hot sample (more energetic) with particles of water from a cold sample (less energetic). As the samples of water mix, the particles of both samples will collide with each other. During these collisions, Heat Energy is transferred between particles. Review: Which “way” will the HE transfer?

Let’s start Part A: Case 1. In this part of the activity, we will mix EQUAL parts of hot and cold water samples together. ANSWER questions #1-#4 on Page 4 in your Blue Lab Book now! 100 ml 100 ml

Melting Ice – Part B You will be able to answer: What is the role of Heat Energy when melting ice? What happens to the particles in solid water (ice) when melting occurs?

How does ice melt? In a solid: the connections between particles are strong, which makes the ice rigid and hard. As we add Heat Energy, the KE of the particles increases and the particles vibrate more violently (faster). If the vibrating motion of the particles is great enough, the bonds between particles begin to break down.

How does ice melt (continued)? The bonds are NOT destroyed, they are weakened, and the particles can now slip past each other. Instead of a rigid solid, the substance now becomes a liquid.

How is the Heat Energy used? When the ice reaches its melting point (zero Celsius) the particles of water need additional energy for the ice to melt. This energy (HE) is used to weaken the bonds between the particles and does NOT increase the KE of the particles.

Part B Follow the directions starting on Page 9, Lab Activity #9. Follow them STEP BY STEP, being SURE to read EVERYTHING! The capital “T” stands for temperature. STOP: right before “Summary of Results” on Page 11.

When a liquid changes (boils) into a gas When enough energy is added to the liquid at the boiling temperature to completely break the bonds that connect the particles (the temperature does NOT change at this point) that make up the liquid, a liquid changes into a gas. The particles are unchanged, but are no longer connected. They are free to move independently and form a gas.

How much energy is needed to COMPLETELY break the bonds of the water particles? How much energy was needed for the ice (solid) to change into water (liquid) in Part B? Well, breaking all of the bonds between the particles in a liquid (so it can change into a gas) takes about SEVEN TIMES as much energy! Let’s put our results on a Change of State Diagram (Page 14 and Handout)…